Chapter 9 The Human Population
9.1: Studying Human Populations • Describe how the size and growth rate of the human population has changed in the last 200 years • Define four properties that scientists use to predict population sizes • Make predictions about population trends based on age structure • Describe the four stages of the demographic transition • Explain why different countries may be at different stages of the demographic transition
2 Categories for Countries: • Countries are often grouped by demographers into 2 general categories: • Developed countries—higher average incomes, slower population growth, and diverse industrial economies. • Developing countries—lower average incomes, simple and agriculture-based economies, and rapid population growth.
Human Population Growth • 1800’s: exponential growth due to… • Increases in food production • Improvements in hygiene (eg. clean water and safe sewage disposal) • Industrial and scientific revolutions • Discovery of vaccines in the 20th century • Cannot continue…limited resources, competition, carrying capacity
Predicting Population Sizes (4) • Age structure • The distribution of ages in a specific population at a certain time. • Graphed in a population pyramid • High growth rate more young than old • Slow or no growth even distribution of ages • Survivorship • The percentage of members of a group that are likely to survive to any given age. • Survivorship curves: type I (most live to be very old), II (similar death rates at all ages), III (very poor, many children die)
Predicting Population Sizes (4) • Fertility rates: the number of babies born each year per 1,000 women in a population. • Also can calculate total fertility rate • Considers “replacement level”: the avg. number of children each parent must have in order to “replace” themselves. • Migration: mvmt. of individuals btwn. areas. • Immigration (in) vs. Emigration (out)
Reasons for Increases in Human Population Growth (or decline)… • Death rates decreased more rapidly than birth rates…causes??? • Life expectancy (most affected by infant mortality); survivorship curve • 1900 = age 40 w/ a high infant mortality rate • 2000 = >age 67 (developed = 80+) w/ infant mortality at < 1/3 of the rate in 1900 • Infant health is affected by… • -parents’ access to education, food, fuel, and clean water • Other threats?: density increases in contagious diseases (e.g. AIDS, tuberculosis, Ebola)
HW!! • Read through chapter 9 • Pg. 239: The Demographic Transition • Take notes over the “stages of transition” and “women and fertility” • Checked in and discussed/questions Monday
9.2 Changing Population Trends • Describe three problems caused by rapid human population growth • Compare population growth problems in more-developed countries and less developed countries • Analyze strategies countries may use to reduce their population growth • Describe worldwide population projections into the next century
3 Problems…cause: rapid human population growth • Primary Problem: environmental; over consumption of resources; infrastructure. • 1. vegetation…ex.: fuelwood • 2. water…used for drinking, washing, &sewage disposal: waterborne diseases such as dysentery, typhoid, and cholera; ex. Lima, Peru. • 3. land…shortage of arable (A.V.) land (land that is used to grow crops); urbanization (A.V.); “suburban sprawl”.
Managing Development and Growth • Strategies used include: family planning programs, economic incentives, legal punishments, public advertising, improvements in women’s status. • Result: worldwide fertility rates are dropping! Demographers predict that by 2050, most countries will have replacement level fertility rates world population growth will _____(?) • World population = >6 billion and is still increasing.